Alternating current lighting system



1942- E. G. DORGELO ETAL 2,292,064

ALTEBNATING CURRENT LIGHTING SYSTEM I Filed May 11, 1940 m 12 6 6 v i s 6 Inventor's: Eduard G. Dot-2e10, Theodor'us Hehenkamp, Fr-ahciscus C, Van L09 T heiw- Abba-hey.

' high impedance for the Patented Aug. 4, 1942 ALTIEIRIZA'IFING CURRENT LIGHTING SYSTEM Eduard Gerardns Dorgelo,

and Franciscus Cornelis Van Looy,

Netherlands, assignors to General Elecp, hoven,

Theodora: Hellen- Eindtric Company, Schenectady, N. Y.

Application May 11, 1940, Serial No. 334,674 In Germany April 17, 1939 3 Claims. (Cl. 176-124) It is known to connect in series with each other and with a stabilization impedance a plurality of gas-filled discharge tubes through the intermediary of transformers and to operate them in this arrangement. In ,this case the primary windings of the transformers feeding the tubes are connected in series. These transformers may be designed as auto-transformers. The stabilization impedance connected in series with the tubes may be designed either as an independent impedance or may be built into a transformer by which its circuit is supplied, the transformer in that case having high leakage reactance. The output of such a transformer may be substantially constant within certain limits.

The term gas-filled discharge tubes is to be understood to mean in the present case not only tubes filled with one or more gases, but also discharge tubes whose filling consists of one or more vapors or of a mixture of gas and vapor.

It will be readily understood that the system comprising the constant current supply means, the stabilization impedance and the discharge tubes can operate with only a certain number of gas-filled discharge tubes of a definite kind. When more tubes are connected in series the drawback occurs that the operation of the tubes is unstable and in the case of the number of tubes being still further increased they can eventually no longer be kept running at all. Furthermore ignition difiiculties occur therewith.

The invention relates to an installation with alternating current feed, more particularly for illumination purposes, which comprises a plurality of transformers whose primary windings are connectw in series with each other and with a stabilization impedance and to whose secondary windings are connected gas-filled discharge tubes.

The object of the invention is to provide means for increasing the number of gas-filled discharge tubes connected in series and for ensuring nevertheless a stable operation, and, if necessary, for assuring also the ignition of th discharge tubes and for obtaining the further advantages stated hereinafter.

As is well known certain harmonics are produced in gas filled discharge tubes. It has been found that unstable operation of such tubes is due to insufficient impedance in the circuit thereof for those harmonics. In accordance with our invention we provide means having third harmonic of the alternating supply current which means consists of inductanc and capacity connected in series with the stabilization impedance of the circuit and with the primary windings of the tube transformers. The impedance means employed while having high impedance to the third harmonic has small impedance at the fundamental frequency.

The impedance means employed is preferably so constructed that the impedance provided thereby in the series circuit for the third harmonic of the alternating feed current, is more than twice as great and preferably more than four times as great as the internal resistance of the discharge tubes. In this case, of course, all values must be compared with each other on the same base. Consequently all values must be considered on the primary side or at the secondary side of the transformers. The expression internal resistance of the gas-filled discharge tubes is, of course, to be understood to mean the sum of the internal resistances of the individual tubes. The said factor, by which this internal resistance should preferably exceed the value, calculated for the third harmonic, of the impedance connected in parallel with the gasfilied discharg tubes depends on the kind of tubes. With sodium-vapor discharge tubes, for instance it amounts to about 4, with mercuryvapor high-pressure discharge tubes to about 2.8 and it can be readily established experimentally for any desired kind of tubes.

The invention will be more clearly understood by reference to the accompanying drawing, showing a circuit diagram of one form of our invention.

The installation represented is fed from the secondary winding 4 of a transformer 2 whose primary winding 3 is connected to a source of alternating current 4, which may be at 220 volts having a frequency of 50 cycles/sec. The installation comprise a plurality of transformers 5 whose primary windings 6 are connected in series with each other and to whose secondary windings I are connected gas-filled discharge tubes 8.

The tubes 8 may be sodium-vapor discharge tubes which are filled with rare gas such as neon under a low pressure and sodium vapor. In the drawing the discharge tubes have incandescent electrodes, not represented, which are heated by ,the discharge to the temperature required for the emission of electrons, although it is also possible to pass a separate heating current through the electrodes in a known manner.

The primary windings 6 are connected, with the interposition of an inductance 9, to the ends of the secondar winding I of the transformer 2 I spatially independent member; in the case of a leakage transformer the inductance 9 consti tutes the leakage-inductance of the transformer 2. In the present cas the transformer 2 and the inductance 9 may together constitute a transformer for the supply of a substantially constant current which transformen as is well known is equippedwith a stationary coil and a coil movable in a perpendicular direction. On the movable coil acts the magnetic repulsive force of the stationary coil as well as its own weight and these forces are kept in equilibrium by a counterweight suspended from a lever arm having a variable length.

The means for impeding the third harmonic is the capacity In and inductances II and It, inserted in series with the stabilization impedance. In parallel with the coil H there is provided the switch l3 whose contacts are closed when the tubes are to be started and opened after the:' i

have started.

In one specific case sixty sodium-vapor discharge tubes could be connected as a result of the use, according to the invention, of the elements Ill, It and ii. In the case described the individual members of the circuit had the following values:

The transformer 2 had a secondary no-load voltage of 1000 volts; it was devised for the supply of a constant current of 10 amperes. Its leakage inductance, denoted by 9 in the giraw'- ing, had an impedance of 20 to 100 ohms at a frequency of 50 cycles/sec. Similarly at a frequency of 50 cycles/sec. the impedances of the condenser I and of the inductances H and I2 amounted to 300, 100 and 200 ohms respectively. The no-load impedance of a transformer had a value of 3 ohms and for all of the sixty transformers this value consequently amounted to 180 ohms at-f=50 cycles/sec. The voltage transformation ratio of the transformers 5 had a value of 16: 1 (secondaryzprimary) The discharge tubes 8 had a maximum running voltage of 212 volts, their discharge current amounting to 0.6 amp. Hence the internal resistance reduced to the primary side of the transformers 5 amounts to 1.37 ohms and the internal resistance of all of the sixty discharge tubes used has a value of 82.5 ohms.

In parallel with the discharge tubes lies the no-load impedance of the transformers 5 and in parallel with this impedance is connected the impedance of the series-connection of the ele'- ments 9, I 0, Hand l2. From the values stated it follows that for the third harmonic of the alternating feed-current, consequently ,f reckoned to be 150 cycles/sec, an impedance of 330 ohms lies in parallel with the internal resistance of the discharge tubes. This impedance of 330 ohms satisfies the condition imposed according to the invention, since it is four times as high as the internal resistance of the discharge tubes together having a value of 82.5 ohms.

As will be appreciated furthermore the total impedance of the. elements It, II and I! for the fundamental frequency of the alternating feed current, vis., when i=5!) cycles/sec. has a value zero so that this condition imposed by the invention is also satisfied. Finally the inductance II also had such an impedance that in the shortcircuited condition of the inductance l l the full series-current of 10 amperes required for ignition of the tubes could flow through the series connection. When using the elements III, II and I2 proporoned and connected according to the invention all of the sixty gas-filled discharge tubes operated with their normal power and did not exhibit any flickering phenomena whatsoever.

-If the elements "l, H and 12 used according to the invention were omitted from the circuit arrangement represented only twenty-six discharge tubes may be ignited and only twentyone discharge tubes may be operated with the normal power. From this it appears that when making use of the expedient according to the invention while utilizing simple means the efficiency of the installation'can be raised more than twice.

said harmonic in Dedance at said What we claim is:

1. An alternating current lighting system comprising a series circuit supplied by a source of constant current and including a plurality of electric discharge lamps subject to the produc tion of a third harmonic of the applied frequency and reactive means for reducing the value of the circuit, said means being constructed to oifer substantially'a minimum imapplied frequency and a high impedance at said third harmonic frequency, the total impedance in said circuit at said third harmonic frequency being more than twice-that in the circuit due to the internal resistance of the lamps.

, 2. An alternating current lighting system comprising a series circuit supplied by a source of constant current and including a plurality of electric discharge lamps subject to the production of a third harmonic of the applied frequency and reactive means for reducing the value of -said harmonic in the circuit, said means comprising inductive and capacitive members arranged in series in said circuit and tuned at said applied frequency but offering a high impedance at said third harmonic frequency, the total impedance in said circuit at said third harmonic frequency being -more than twice that in the circuit due to the internal resistance of the lamps.

3. An alternating current lighting system comprising a series circuit supplied by a source of constant current and having inductive stabilization impedance, said circuit including a plurality of electric discharge lamps subject to the production of a third harmonic of the applied frequency and reactive means for reducing the value of said harmonic in the circuit, said means comprising a capacitor and a reactor having a plurality of parts arranged in series and tuned at said applied frequency, the total impedance in said circuit at said third harmonic frequency being more than four times that in the circuit due to the internal resistance of the lamps and a switch for short circuiting one of the parts of said reactor .to start the lamps.

EDUARD GERARDUS DORGELO. THEODORUS FRANCISCUS CORNELIS VAN LOOY. 

